feat: platform back button add

lib/platform_ui.dart

@@ -23,3 +23,4 @@ export 'src/platform_text.dart';
 export 'src/platform_alert_dialog.dart';
 export 'src/platform_checkbox.dart';
 export 'src/platform_builder.dart';
+export 'src/platform_back_button.dart';

lib/src/platform_back_button.dart

@@ -0,0 +1,50 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:macos_ui/macos_ui.dart';
+import 'package:platform_ui/platform_ui.dart';
+
+class PlatformBackButton extends StatelessWidget with PlatformMixin<Widget> {
+  final Color? color;
+  final VoidCallback? onPressed;
+  const PlatformBackButton({Key? key, this.color, this.onPressed})
+      : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return getPlatformType(context);
+  }
+
+  @override
+  Widget android(BuildContext context) {
+    return BackButton(
+      color: color,
+      onPressed: onPressed,
+    );
+  }
+
+  @override
+  Widget ios(BuildContext context) {
+    return CupertinoNavigationBarBackButton(
+      color: color,
+      onPressed: onPressed,
+    );
+  }
+
+  @override
+  Widget linux(BuildContext context) {
+    return android(context);
+  }
+
+  @override
+  Widget macos(BuildContext context) {
+    return MacosBackButton(
+      fillColor: color,
+      onPressed: onPressed,
+    );
+  }
+
+  @override
+  Widget windows(BuildContext context) {
+    return android(context);
+  }
+}

lib/src/platform_drop_down_menu.dart

@@ -153,8 +153,8 @@ class _PlatformDropDownMenuState<T> extends State<PlatformDropDownMenu<T>>
         mainAxisSize: MainAxisSize.min,
         children: [
           widget.items[index].ios(),
-          const SizedBox(width: 8),
-          const Icon(CupertinoIcons.chevron_down_circle),
+          const SizedBox(width: 4),
+          const Icon(CupertinoIcons.chevron_down),
         ],
       ),
       onPressed: () {

lib/src/platform_slider.dart

@@ -120,6 +120,7 @@ class PlatformSlider extends StatelessWidget with PlatformMixin<Widget> {
         inactiveColor: inactiveColor != null
             ? FluentUI.ButtonState.all(inactiveColor)
             : null,
+        margin: const EdgeInsets.all(8),
       ),
       mouseCursor: mouseCursor,
       focusNode: focusNode,

lib/src/specific/cupertino_list_tile.dart

@@ -502,7 +502,7 @@ class CupertinoListTile extends StatelessWidget {
 
     if (selected) return theme.primaryColor;
 
-    return null;
+    return theme.primaryColor;
   }
 
   Color? _textColor(BuildContext context, PlatformThemeData theme,